1. Field of the Invention
This invention relates to a vehicle suspension system, and more particularly to a vehicle suspension system for supporting dirigible wheels of a vehicle.
2. Description of the Prior Art
As the vehicle suspension system for supporting the dirigible wheels, there have been known a wishbone type suspension in which upper and lower ends of each wheel support member for supporting a dirigible wheel for rotation are connected to the vehicle body respectively by way of upper and lower arms extending in the transverse direction of the vehicle body, and a strut type suspension in which a strut is used for connecting the upper end of the wheel support member to the vehicle body in place of the upper arm in the wishbone type suspension. See Japanese Patent Publication No. 52(1977)-9889, for example.
The dirigible wheels supported by such a suspension system should be controlled, in order to increase the road gripping force and to improve the turning performance, so that the inner wheel has a positive camber and the outer wheel has a negative camber when they are making a turn. As a means for controlling the camber of the dirigible wheels during turning in the manner described above, there has been known an arrangement disclosed in Japanese Unexamined Patent Publication No. 58(1983)-67508 in which a pair of link members forming the upper arm are disposed so that the axis of symmetry thereof is set at an acute angle to the wheel axis and is positioned on the rear side of the wheel axis, and the imaginary kingpin axis (imaginary pivot axis) of the outer wheel is moved rearward to increase the caster angle so that the outer wheel has a negative camber.
However, the arrangement described above is disadvantageous in that it can be applied only to a wishbone type suspension system having an upper arm formed of a pair of link members and a lower arm formed of a so-called A-shaped arm Further, since the two link members must be disposed so that the axis of symmetry thereof is set at an acute angle to the wheel axis, one of the link members must be connected to the vehicle body at a substantially outer portion of the vehicle body. This makes it difficult to apply the arrangement to conventional vehicles, as they are.
Further, there have been disclosed in U.S. Pat. No. 4,440,420, and Japanese Patent Publication Nos. 51(1976)-20765 and 52(1977)-9889 suspension systems in which the wheel can be provided with a negative camber when it makes a turn as the outer wheel. However, in any one of the suspension systems, the wheel cannot be provided with a positive camber when it makes a turn as the inner wheel.